Conformational Entropy as a Means to Control the Behavior of Poly(diketoenamine) Vitrimers In and Out of Equilibrium. Issue 2 (21st November 2019)

• Record Type: Journal Article
• Authors: He, Changfei; Christensen, Peter R.; Seguin, Trevor J.; Dailing, Eric A.; Wood, Brandon M.; Walde, Rebecca K.; Persson, Kristin A.; Russell, Thomas P.; Helms, Brett A.
• Is Part Of: Angewandte Chemie international edition. Volume 59:Issue 2(2020)
• Page Start: 735
• Page End: 739
• Publication Date: 2019-11-21
• Subjects: conformational entropy -- mechanical properties -- poly(diketoenamine) -- rheology -- vitrimers; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201912223
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: Control of equilibrium and non‐equilibrium thermomechanical behavior of poly(diketoenamine) vitrimers is shown by incorporating linear polymer segments varying in molecular weight (MW) and conformational degrees of freedom into the dynamic covalent network. While increasing MW of linear segments yields a lower storage modulus at the rubbery plateau after softening above the glass transition (Tg ), both Tg and the characteristic time of stress relaxation are independently governed by the conformational entropy of the embodied linear segments. Activation energies for bond exchange in the solid state are lower for networks incorporating flexible chains; the network topology freezing temperature decreases with increasing MW of flexible linear segments but increases with increasing MW of stiff segments. Vitrimer reconfigurability is therefore influenced not only by the energetics of bond exchange for a given network density, but also the entropy of polymer chains within the network. Abstract : Go with the flow : Microstructural and architectural attributes of vitrimers are powerful design elements for controlling their mechanical and rheological properties. Conformational entropy of their embodied monomer segments appears to dominate such properties for architecturally similar vitrimer networks.